The present invention relates to a vector processor and more particularly, to a vector processor suitable for extending an address space.
A vector processor is generally constructed of a scalar processing unit, a vector processing unit and a main storage accessible by both the processor units. The scalar processing unit executes instructions of the same type as those used by a general purpose computer, whereas the vector processing unit executes vector instructions to perform vector processing.
The application fields of vector processors will expand in the future. The performance of vector processors will need to be much improved and, at the same time, the expansion of address space will be needed. To realize high speed operation, the main storage of a vector processor is made up of high speed memory devices. Therefore, if a main memory of a large capacity is used to extend an address space, the cost of the vector increases In consideration of such high cost, an extended storage using low speed and high capacity memory devices as an external storage is disclosed, for example, in U.S. Pat. No. 4,630,230, issued Dec. 16, 1986.
An extended storage used as an external storage can provide a large address space at lower cost than that obtained by a main storage only. However, this arrangement poses some restrictions in that the extended storage uses lower speed memory devices than the main storage, and it must be located at a position farther from the CPU than the main storage. Therefore, the data transfer speed is lower. If the lower data transfer speed is intended to be recovered by changing the transfer data length, the consistency with the data processing unit of the CPU is lost. In view of this, in some case, the data processing at the CPU is separated in the time domain from the data transfer processing to and from the main storage and the extended storage. Thus the main storage is used as a local memory. With this method, however, user programs must support time separation of both the processings, and the data buffer processing. As a result, the logical structure of programs becomes complicated. Thus, the problem of difficult understanding of programs and a lack of versatility of programs ensues.